LIDAR reference waveforms with increased sample rates.

Abstract

To provide a method and system for determining a distance to a target region in an optical detection system.SOLUTION: A method for determining a distance to a target region in an optical detection system includes acquiring first and second light pulses from a signal generator within the optical detection system and acquiring samples of the respective first and second light pulses, and the samples have a first temporal resolution. The method also includes generating a reference waveform having a second temporal resolution by combining the samples of the respective first and second light pulses, and the second temporal resolution is higher than the first temporal resolution. The method further includes acquiring the reflection of a third light pulse from the target region and determining an arrival time of the reflection of the third light pulse using the reference waveform.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This document relates generally, but not exclusively, to improving accuracy in LIDAR systems. [Background technology]

[0002] Certain laser ranging systems are based on time-of-flight measurements, for example, in systems where the absolute time between a transmitted signal and a received signal is measured and used to determine the distance to a target object or area of ​​interest (hereinafter, "target area"). In one example, a pulsed LIDAR system calculates the distance to the target area by transmitting a series of light pulses toward the target area and determining the time-of-flight of the returned pulses. Determining the time-of-flight of the returned pulses may include digitizing the entire waveform, including noise and the returned pulses, and performing an echo detection operation using the digitized waveform to identify the returned pulses within the noise. The determined time-of-flight of the pulses is then used to determine the distance from the LIDAR system to the target area. Summary of the Invention [Means for solving the problem]

[0003] A method for determining distance to a target area in an optical detection system can include acquiring first and second light pulses from a signal generator in the optical detection system and acquiring samples of each of the first and second light pulses, the samples having a first temporal resolution. The method can also include generating a reference waveform having a second temporal resolution by combining the samples of each of the first and second light pulses, the second temporal resolution being higher than the first temporal resolution. The method can further include acquiring a reflection of a third light pulse from the target area and using the reference waveform to determine the arrival time of the reflection of the third light pulse.

[0004] A method for determining a distance to a target area in an optical detection system can include acquiring first and second light pulses from an optical transmitter and providing the first and second light pulses to a first detector in the optical detection system. The method can also include adjusting a sample time of the second light pulse to create a time delay between capturing a sample of the first light pulse and capturing a sample of the second light pulse at the first detector, and capturing samples of each of the first and second light pulses at the first detector based on the adjusted sample time. The method can further include acquiring a temporal profile of the captured samples, transmitting a third light pulse to the target area, and receiving a reflection of the transmitted third pulse from the target area at a second detector. The method can additionally include determining a time of arrival of the received reflection based on the temporal profile.

[0005] An optical ranging system for determining a distance to a target area can include a transmitter circuit for generating first and second optical pulses, a first optical detection circuit for converting the first and second optical pulses into respective first and second electrical signals, and a sampling circuit coupled to the first optical detector for acquiring samples of the electrical signals. The system can also include a modulation circuit coupled to the sampling circuit, the modulation circuit activating the sampling circuit to acquire a first sample of the first electrical signal according to a first sampling trigger and to acquire a second sample of the second electrical signal according to a second sampling trigger, the first sampling trigger being offset in time from the second sampling trigger by a timing delay corresponding to a fraction of a sampling period of the first detector. The system can further include a synthesizer circuit for interleaving the first and second samples to generate a reference waveform, thereby acquiring a reference waveform having a higher resolution than the sampling resolution of the first detection circuit. The system can additionally include a signal detection circuit for determining the arrival time of a reflection of a third optical pulse from the target area based on the reference waveform.

[0006] This Summary is intended to provide an overview of the subject matter of this patent application. It is not intended to provide an exclusive or exhaustive description of the invention. The Detailed Description is included to provide further information regarding this patent application. [Brief explanation of the drawings]

[0007] In the drawings, which are not necessarily drawn to scale, like numerals may describe like components in different drawings. Like numerals with different letter suffixes may represent different instances of like components. The drawings generally illustrate, by way of example, but not by way of limitation, various embodiments discussed in this document.

[0008] [Figure 1] FIG. 1 shows an example of a LIDAR system that uses a reference waveform to determine the time of flight of a signal. [Figure 2A] 2A-2D show diagrams of electrical pulses that are sampled to generate a reference waveform. [Figure 2B] 2A-2D show diagrams of electrical pulses that are sampled to generate a reference waveform. [Figure 2C] 2A-2D show diagrams of electrical pulses that are sampled to generate a reference waveform. [Figure 2D] 2A-2D show diagrams of electrical pulses that are sampled to generate a reference waveform. [Figure 3] FIG. 3 shows an example of filtering the generated reference waveform. [Figure 4] FIG. 4 shows an example of processing a reflected signal using a generated reference waveform. [Figure 5] FIG. 5 shows an example of how a LIDAR system operates. DETAILED DESCRIPTION OF THE INVENTION

[0009] This disclosure includes techniques for improving the timing or distance measurement resolution of LIDAR systems without requiring improvements to the analog-to-digital converters (ADCs) used in such systems. Such improvements are obtained by synthesizing a high sample rate reference waveform using a low sample rate ADC used in conjunction with a matched filter to determine the time of flight of a signal transmitted to a target area. These techniques can reduce the cost of LIDAR systems by enabling high-resolution time-of-flight or distance measurements in systems that use slow or low sample rate ADC circuits.

[0010] Optical ranging systems, such as LIDAR, use the time-of-flight principle to measure distance. According to the time-of-flight principle, the round-trip transit time of a pulse of light is equal to 2*d / c, where d is the distance to the target and c is the speed of light. Consequently, the minimum resolvable distance, Δd, is related to the minimum resolvable time difference, ΔT, by the same relationship: Δd = c*ΔT / 2. For this reason, LIDAR systems typically rely on high-sample-rate ADCs in the receive signal chain, since the sample rate of the ADC determines the minimum resolvable time difference. As an example, a 1 gigasamples-per-second (GS / s) ADC samples at 1 nanosecond (ns) intervals. If a 1-ns time interval is the same as the minimum resolvable time difference, as in conventional LIDAR systems, the corresponding resolvable distance is Δd = 15 cm. From a cost, power, and complexity perspective, it is desirable to use an ADC with a lower sample rate while maintaining comparable or better range resolution. Equally, it is desirable for the LIDAR system to be constructed so that the smallest resolvable time difference is less than the sampling interval of the ADC.

[0011] A LIDAR system can use a matched filter to detect LIDAR signals of a noisy waveform reflected from a target area. In one example, a reference waveform is convolved with a noisy waveform reflected from the target area (hereinafter, the "reflected waveform") to identify points or areas of maximum overlap between the reference waveform and the reflected waveform. The identified overlap points can be used to determine the time of flight of the transmitted LIDAR signal, and by extension, the distance measurement from the LIDAR system to the target area, as described in U.S. Patent Publication No. 2020-0041651 A1 to Kapusta et al., entitled "System and Method for Improving Range Resolution in a Lidar System," which is incorporated by reference in its entirety. The accuracy or resolution of the distance measurement can depend on the temporal resolution at which the point of maximum overlap between the reference waveform and the reflected waveform is determined. The temporal resolution at which the point of maximum overlap between the reference waveform and the reflected waveform is determined can depend on the temporal resolution of the reference waveform or the temporal resolution of the reflected waveform. One technique for improving the resolution of the reference waveform or the detected return signal, and by extension the resolution of the range measurement, is to use faster detection or sampling circuitry, such as a high sample rate analog-to-digital converter, digitizing the reference LIDAR pulse used to acquire the reference waveform, or digitizing the return waveform. However, such techniques may increase the cost or power consumption of the LIDAR system.

[0012] Embodiments of the present disclosure are based on the recognition that for a LIDAR system configured with a reference channel having a sampling circuit, such as an ADC, with a specified sample rate, a reference waveform can be synthesized having a resolution higher than the sampling rate of the sampling circuit. Such a reference waveform can be generated by acquiring digital samples of two or more sets of optical pulses generated by the LIDAR system, each set of digital samples corresponding to a LIDAR pulse generated by the system, by changing or adjusting the sample time or sample trigger for operating the sampling circuit to acquire the digital samples relative to the sample time or sample trigger used to acquire digital samples of another LIDAR pulse. The sets of digital samples can then be combined, for example, by interleaving samples of different pulses, and processed to acquire a reference waveform having sample data points between the nominal sample periods of the sampling circuit. In one embodiment, the sample time or sample trigger is changed or adjusted by delaying one sample time relative to another by a fraction of the sample period of the sampling circuit. In one example, adjusting the sample time for acquiring the digital sample of the first LIDAR pulse includes adjusting the time at which the sampling circuitry is activated to begin capturing the digital sample, for example, by delaying a trigger or clock signal that initiates the sampling. The timing adjustment and sampling operation can be repeated for one or more LIDAR pulses, for example, by applying different timing delays to the sample time of each pulse, and the resulting digital samples can be combined to synthesize a reference waveform with increased time resolution (e.g., decreased time or temporal distance between sample data points).

[0013] As used herein, a sample time is a time relative to a reference signal or clock at which a sampling circuit is operated to obtain a set of one or more digital samples of an electrical signal. In one embodiment, a first sample time for obtaining a first set of digital samples is a time relative to a first pulse of the reference signal or clock, and a second sample time for obtaining a second set of digital samples is a time relative to a second pulse of the reference signal or clock.

[0014] FIG. 1 illustrates an example of a LIDAR system 100 that uses a reference waveform to determine the time-of-flight of a signal, such as an electromagnetic or optical pulse (hereinafter, "optical pulse" or "LIDAR pulse") transmitted by the LIDAR system. In one example, the LIDAR system 100 is a scanning LIDAR system configured to incrementally generate an image of a target area within a field of view of the LIDAR system by transmitting a series of LIDAR pulses toward the target area and determining the time-of-flight of the reflected LIDAR pulses. The LIDAR system 100 may include a transmitter circuit 105, a reference circuit 120, and a receiver circuit 170. In another example, the LIDAR system 100 is a flash LIDAR system that generates an image of a portion or the entire field of view without scanning the transmitted light. As a flash system, the receiver circuit 170 may be replicated multiple times, each processing a portion of the reflected LIDAR pulses.

[0015] The transmitter circuit 105 includes circuitry configured to generate or transmit one or more LIDAR pulses, e.g., toward a set of one or more target areas, to determine the distance to the target areas. In one embodiment, the transmitter circuit includes an illuminator 110 and a splitter 115. The illuminator 110 can include any suitable light-emitting device, such as a laser or a light-emitting diode. In one embodiment, the illuminator 110 is configured to generate a coherent light beam, such as a laser pulse, including light of a designated frequency or set of frequencies. The splitter 115 can include any device configured to direct the LIDAR pulses generated by the illuminator 110 to a first aperture (not shown) of the LIDAR system 100, e.g., for transmission to the target areas. The splitter 115 can also be configured to direct the LIDAR pulses 117, or a portion of the LIDAR pulses, to a detector 125 in the reference circuit 120. In one embodiment, the splitter 115 includes a lens, a prism, an optical waveguide, or a mirror. In one embodiment, splitter 115 is not an explicit component of transmitter circuitry 105. In this embodiment, LIDAR pulse 117 is stray or parasitic light scattered from the transmitted LIDAR pulse by other components within transmitter 105. In a scanning LIDAR system, transmitter circuitry 105 may also include an optical steering element, such as a mirror, a MEMS mirror, a rotating reflective polygon, an optical phased array, a liquid crystal beam steerer, or another steering element.

[0016] Reference circuit 120 includes circuitry configured to synthesize or generate a reference waveform in accordance with the techniques described herein. In one example, reference circuit 120 includes detector 125, sampling circuit 130, reference waveform generator 145, and filter 165. Detector 125 includes circuitry configured to detect or capture optical pulses, such as LIDAR pulses, directed to reference circuit 120 by splitter 115 and generate an electrical signal (e.g., a time-varying voltage, current, or frequency) indicative of the detected optical pulse. In one example, detector 125 includes a photodiode, an avalanche photodiode (APD), a phototransistor, a single-photon detector, or any other suitable photosensitive device.

[0017] Sampling circuit 130 includes a circuit, or a signal chain including one or more circuits, configured to generate a digital representation of the electrical signal generated by detector 125 (e.g., an electrical signal representing a detected optical pulse). The digital representation of the electrical signal may include discrete voltages or a series of one or more digital values ​​representing an electrical characteristic or signal. In one embodiment, sampling circuit 130 generates a set of discrete voltages representing a binary or binary-coded decimal representation of the magnitude of the voltage or current corresponding to the optical pulse detected by detector 125. In another embodiment, sampling circuit 130 generates a set of discrete electrical pulses representing a binary or binary-coded decimal representation of the frequency of the optical pulse detected by detector 125. In another embodiment, sampling circuit 130 generates a set of discrete electrical pulses representing a binary or binary-coded decimal representation of the time at which the optical pulse was detected by detector 125.

[0018] Sampling circuit 130 may include conditioning circuit 135 and converter circuit 140. Conditioning circuit 135 includes circuitry configured to convert a first electrical signal, such as an input reference signal generated by detector circuit 125, into a second electrical signal, such as a conditioned reference signal that meets one or more input signal condition requirements for converter circuit 140. In one embodiment, conditioning circuit 135 is a transimpedance amplifier (TIA) configured to convert the input reference signal, which includes a current indicative of the optical pulse detected by detector 125, into a conditioned reference signal, which includes a voltage that corresponds to the current or is generated using the current.

[0019] Converter circuit 140 includes circuitry configured to digitize an electrical signal, such as the analog conditioned reference signal generated by conditioning circuit 135. In one embodiment, converter circuit 140 includes a low sample rate ADC, such as an ADC with a sampling rate of less than 500 million samples per second (MSPS). Such an ADC traditionally corresponds to the use of a 1 GS / s ADC, which is considered a low sample rate for a LIDAR system achieving a range resolution of 15 centimeters (cm) or better. Converter circuit 140 can be configured to capture or digitize samples of the conditioned reference signal based on timing indicated by a clock or other trigger signal. In one embodiment, converter circuit 140 is configured to periodically capture or digitize samples of the conditioned reference signal at a time relative to a rising or falling edge of the clock or trigger signal. In one embodiment, system 100 causes converter circuit 140 to capture or digitize samples of the conditioned reference signal or activates converter circuit 140 to do so by activating a control signal for the converter circuit in response to or using the clock or trigger signal. The clock or trigger signal may be generated based on one or more timing parameters or timing circuits of the LIDAR system 100. In one example, the clock or trigger signal is generated or configured to cause the converter circuit to sample or digitize the conditioned reference signal in coordination with the transmission of one or more LIDAR pulses toward a target area, for example, by causing the converter circuit to initiate or perform a series of sampling operations at designated times relative to the transmission of the LIDAR pulses.

[0020] In some embodiments, the detection circuit 125 and the sampling circuit 130 may be combined into a single circuit, such as a digital output sensor. As some examples, the digital output sensor may be a CMOS image sensor, a silicon photomultiplier, or a single-photon avalanche diode (SPAD) sensor.

[0021] The reference waveform generator 145 includes one or more circuits configured to generate or synthesize a reference waveform (e.g., a composite reference waveform) based on the LIDAR pulses detected by the detection circuit 125. In one example, the reference waveform generator 145 receives a set of one or more digital samples from the sampling circuit 130 and generates the reference waveform by using interpolation, interleaving, or other suitable techniques for extrapolating points on the composite waveform between the digital samples. The output of the reference waveform generator 145 may include data indicative of a reference waveform that indicates a temporal profile of the optical pulse detected by the detector 125. In one example, the temporal profile of the optical pulse includes a time-varying representation of the optical pulse, such as a waveform or series of sample data points representing the amplitude of a current or voltage as a function of time. The fidelity or resolution of the reference waveform may be determined based on the temporal or time-based distance between adjacent digital samples in the set of one or more digital samples; thus, a shorter temporal distance between digital samples produces a higher-fidelity reference waveform that corresponds to improved distance resolution when used in time-of-flight calculations.

[0022] The reference waveform generator 145 includes a control circuit 150, a memory 155, and a synthesizer 160. The control circuit 150 can be configured to control the operation of one or more components of the waveform generator 145, for example, to acquire digital samples from the sampling circuit 130, store the acquired samples in the memory 155, or operate the synthesizer 160 to generate one or more reference waveforms using the stored digital samples. The control circuit 150 can also be configured to generate or adjust clock or trigger signals relative to each other used by the sampling circuit 130 and the transmitter 105 to initiate a set of sampling operations to generate digital samples of signals such as transmit pulses and conditioned reference signals. Generating or adjusting the clock or trigger signal can include delaying or offsetting the clock or trigger signal by a fraction of a sampling period of the sampling circuit 130 or an ADC associated with the sampling circuit. In one embodiment, the control circuit 150 is configured to generate a first clock or trigger signal (e.g., a reference trigger) to cause the sampling circuit 130 to generate a first set of digital samples, each spaced apart by an integer number of sampling periods from the first clock or trigger signal. The control circuit 150 can be configured to generate a second clock or trigger signal having a first delay, such as a delay that is one-seventh of the determined sampling period of the sampling circuit 130 relative to the first clock or trigger signal, to cause the sampling circuit 130 to generate a second set of digital samples, each spaced apart by an integer number of sampling periods from the second clock or trigger signal. Such second set of digital samples is delayed or offset by the first delay with respect to the first set of digital samples. In one embodiment, the first set of digital samples is obtained from a first optical pulse detected by the detector 125, and the second set of digital samples is obtained by sampling a second optical pulse detected by the detector.

[0023] The synthesizer circuit 160 is configured to obtain two or more sets of digital samples, such as a first set of digital samples and a second set of digital samples including samples delayed relative to corresponding samples in the first set of digital samples, e.g., from memory 155, and combine the samples to generate a composite waveform having a higher time resolution than the sampling circuit 130. In one embodiment, the synthesizer circuit 160 can obtain seven sets of digital samples, each delayed by a different time kΔT, where k is an integer between 0 and 6, and ΔT is a time span corresponding to one-seventh of the sampling period of the sampling circuit 130. The synthesizer circuit 160 can combine the seven sample sets to generate an aggregate sample set. The aggregate sample set can then be used to synthesize a waveform having seven times higher resolution than the resolution sampling circuit that generated the set of digital samples. In another embodiment, the synthesizer 160 is a process implemented by one or more circuits, such as a microprocessor. Such a process includes storing a set of digital samples in memory 155 and sequentially retrieving interleaved subsets of the stored samples, where the digital samples in the interleaved subsets are interleaved based on their sample times. In one embodiment, the set of digital samples is interleaved and stored in memory 155. In another embodiment, the set of digital samples is interleaved after being stored in memory 155 according to a memory access operation, for example, performing an interleaved memory read.

[0024] Filter 165 includes circuitry, such as a low-pass filter, configured to filter or remove noise from a reference waveform, such as the reference waveform generated by waveform generator 145. In one example, filter 165 includes an averaging filter configured to acquire or receive two reference waveforms and combine the waveforms, for example, by averaging, to generate a noise-reduced reference waveform. In another example, filter 165 includes a process for filtering or reducing noise by averaging or weighting two or more sets of digital samples. In one example, two different sets of digital samples with the same timing delay may be averaged together to reduce noise. This noise reduction can continue to improve as additional sets of digital samples are acquired during operation of LIDAR system 100.

[0025] Receiver circuit 170 includes one or more circuits forming a signal chain for detecting and processing LIDAR signals reflected from a target area. In one embodiment, receiver circuit 170 includes detection circuit 180, sampling circuit 190, and filter circuit 197. The detector is configured to receive reflected LIDAR pulses and provide electrical signals indicative of the received LIDAR pulses to sampling circuit 185. Sampling circuit 185 is configured to process the electrical signals indicative of the received LIDAR pulses, for example, through operation of conditioning circuit 190 and converter circuit 195, to generate a digitized representation of the electrical signal. Filter 197 includes one or more circuits configured to process the digitized representation of the electrical signal, for example, to reduce or remove noise.

[0026] Signal detector 175 includes circuitry configured to identify reflected LIDAR pulses using signals or waveforms generated or produced by reference circuit 120 and receiver circuit 170. In one example, identifying the reflected LIDAR pulses includes determining the time-based position of the pulses or the position of the peaks of the pulses within the signals generated by receiver circuit 170. In another example, identifying the reflected LIDAR pulses includes obtaining or determining an amplitude plot or time profile of the reflected LIDAR pulses within the signals generated by receiver circuit 170. Signal detector 175 includes a matched filter configured to use, for example, the reference waveforms generated by reference circuit 120 as a reference or template signal for identifying LIDAR pulses within the digitized received signals generated by receiver circuit 170. If a matched filter is used in signal detector 175, noise reduction filters 165, 197, or both, may be components or elements of the matched filter.

[0027] In operation, illuminator 110 generates a set of one or more LIDAR pulses that are each split by beam splitter 115 to form a transmit pulse 116 and a reference pulse 117. In some embodiments, rather than using beam splitter 115, reference pulse 117 is obtained from light of the LIDAR pulse scattered by one or more components of the LIDAR system. 116is transmitted to the target area, for example, through an optical lens, and reference pulse 117 is routed to detector 125. In one embodiment, a portion of transmit pulse 116 is reflected from the target area and detected by detector 180 in received signal 176. In one embodiment, when the target area is within the detection range of LIDAR system 100 or when the target area reflects its transmit pulse at a favorable angle to the LIDAR system, the reflected portion of transmit pulse 116 is only present in received signal 176 and therefore only detectable by detector 180. However, reference pulse 117 remains within LIDAR system 100 and is therefore always detectable by detector 125, improving the quality of the reference waveform even when return signal 176 is weak, noisy, or absent. Sampling circuitry 130 samples each detected reference pulse at one or more points along the pulse waveform to generate a set of digitized samples indicative of the points on the waveform corresponding to the detected reference pulse.

[0028] In one embodiment, the transmitter 105 generates LIDAR pulses according to a system trigger signal, such as a reference clock. The sampling circuit 130 can initiate a sampling sequence according to a sampling trigger signal that is offset from the system trigger signal, for example, by a fraction of the sampling circuit's sampling period. The offset can be adjusted to allow the sampling circuit 130 to sample two or more reference pulses at different offsets and generate two or more sets of corresponding digitized samples, with each set of digital samples corresponding to samples of a different reference pulse. In one embodiment, samples are acquired at the sampling circuit's maximum sampling rate. The reference waveform generator 145 can then combine or use the two or more sets of digitized samples to generate a composite waveform with a time resolution higher than the sampling rate of the sampling circuit 130. In one embodiment, two or more composite waveforms are generated over time and can be used by the filter 165 to remove noise or perform other processing. The composite waveform can then be used to detect reflected portions of the transmitted pulse 116 in the received signal 176, for example, in a convolution operation implemented by a matched filter circuit.

[0029] 2A-2D show diagrams of electrical pulses that are sampled to generate a composite reference waveform or signal, for example, as described in the discussion of FIG. 1. In one example, each electrical pulse shown in FIGS. 2A-2D is an example of a different reference pulse, such as reference 117, generated by transmitter 105 and detected by detector 125. In one example, the electrical pulses are transmitted by the transmitter over a time span during an operating LIDAR system, such as system 100. Each pulse can be sampled at a designated offset relative to a reference trigger 210 (e.g., a system trigger signal).

[0030] FIG. 2A shows a first electrical pulse 205 and a sampling interval T S2 shows a set of digital samples 215, 220, and 225 of a first electrical pulse taken at a sampling interval T S may indicate the minimum sampling time or interval of a sampling circuit that generates digital samples. As shown in FIG. 2A, the first sample 215 is captured at a time interval (hereinafter "interval") after a reference trigger 210, and each subsequent sample 220 and 225 is captured at least T after the capture of the previous sample. S In one embodiment, the first sample coincides with or is minimally delayed from the reference trigger.

[0031] 2B shows a second electrical pulse 230 and a set of digital samples 235, 240, and 245 of the second electrical pulse. As shown in FIG. 2B, the second sample 235 is taken at a time T S +ΔT (e.g., sampling begins or the first sample is acquired), and each subsequent sample 240 and 245 is acquired at least T after the acquisition of the immediately preceding sample. S The time +ΔT is the offset or delay for triggering the sampling sequence relative to the reference trigger 210. In one embodiment, the offset is the sampling interval T S The offset +ΔT is the fraction of the time that the first sample 235 is offset by T relative to the reference trigger 210. S +ΔT and the second sample 240 is taken at 2T S The third sample is taken at +ΔT and the second sample is taken at 3T. S The sampling sequence is delayed so that it is taken at +ΔT.

[0032] 2C shows a third electrical pulse 250 and a set of digital samples 255, 260, and 265 of the third electrical pulse. As shown in FIG. 2C, the third sample 235 is taken at a time T S +2ΔT, and each subsequent sample 260 and 265 is acquired at an interval or at least T after the acquisition of the previous sample. SThe time +2ΔT is an offset or delay for triggering the sampling sequence relative to the reference trigger 210. In one embodiment, the offset +2ΔT is twice the duration of the offset discussed in FIG. 2B. In another embodiment, the offset +2ΔT is an offset that is greater or less than the offset discussed in FIG. 2B. The offset +2ΔT is the offset at which the first sample 255 is captured relative to the reference trigger 210. S +2ΔT and the second sample 260 is taken at 2T S The third sample was taken at +2ΔT and the third sample was taken at 3T. S The sampling sequence is delayed so that it is taken at +2ΔT.

[0033] 2D shows an aggregation of the samples described in FIGS. 2A-2C. In one example, the aggregated samples have a time resolution of ΔT. The aggregated samples can be used to generate a composite reference waveform, for example, by reference waveform generator 145, as described herein.

[0034] FIG. 3 illustrates an example of filtering a composite reference waveform. As shown in FIG. 3, two or more reference waveforms 305 can be processed by filter 310 to generate filtered reference waveform 315. Filter 310 is an example of filter 165 (FIG. 1). In one example, two or more composite reference waveforms 305 are generated by reference waveform generator 145. Filter 310 can be an example of filter 156 and can be configured to generate filtered reference waveform 315 by averaging two or more reference waveforms 305 or by using any other suitable filtering technique. In one example, the averaging time constant can be selected or adapted to obtain a specified level of noise reduction while maintaining the ability of the reference waveform to track dynamic changes, such as temperature and power supply fluctuations, that may affect the shape of the reference waveform. A larger averaging time constant can result in greater noise reduction, but also reduces the ability of the reference waveform to track dynamic changes. A shorter averaging time constant can result in greater ability to track dynamic changes, at the expense of reduced noise reduction.

[0035] FIG. 4 illustrates an example of processing a reflected signal using a synthesized reference waveform. A signal chain, such as receiver circuit 170, can obtain a digital sample set 405 of the reflected signal by performing low-time resolution measurements of the reflected signal using a low-sample-rate sampling circuit, such as sampling circuit 130. An interpolator circuit 410 can process the digital sample set 405 to generate an enhanced digital sample set 415, for example, by using polynomial interpolation or another data interpolation technique. The enhanced digital sample set 415 can include the digital samples 405 and a set of estimated digital samples determined from the digital samples 405. In one example, the interpolator circuit 410 uses digital upsampling and interpolation to match the number of samples in the enhanced digital sample set 415 to the sample rate of a synthesized reference waveform 420. The synthesized reference waveform 420 can include a high-sample-rate reference waveform, such as that generated by reference circuit 120. A matched filter 425 can then use the reference waveform 420 to process the enhanced digital sample set 415 to, for example, determine the position or time of arrival of a LIDAR pulse within the reflected signal. According to these techniques, the position or time of the LIDAR pulse within the reference signal can be determined with an accuracy comparable to the time resolution or sample rate of the synthesized reference waveform.

[0036] 5 illustrates one example of operations 500 for operating a LIDAR system. In one example, operations 500 are implemented or performed by a system configured using one or more components of LIDAR system 100, for example, to improve the timing or ranging resolution of the LIDAR system in accordance with the techniques described herein.

[0037] At 505, a set of one or more light pulses is obtained from a light pulse emitter or transmitter circuit, such as transmitter 105. In one embodiment, obtaining the set of light pulses includes activating an illuminator, such as illuminator 110, to emit one or more light pulses and processing the emitted light pulses through an optical device, such as splitter 115, to split or divide each light pulse into a first light pulse 116 and a second light pulse 117.

[0038] At 510, a first set of one or more light pulses is transmitted to and received by a light pulse detection circuit (hereinafter "detection circuit"), such as detector 125, for example, by using a mirror, other optical reflector, or optical waveguide, or by geometric optical design. The detection circuit generates an electrical signal indicative of the first set of light pulses. In one example, the electrical signal indicates the time-varying intensity of each pulse in the first set of light pulses. The first set of light pulses is transmitted to and received by the detector regardless of whether the LIDAR system transmits light pulses to a target area or receives reflections of light pulses from the target area. The electrical signal generated by the detection circuit is then provided to a digital sampling circuit, such as sampling circuit 130.

[0039] At 515, the electrical signal generated by the detection circuit is sampled by a digital sampling circuit. In one example, a first partial electrical signal indicative of the first light pulse is sampled by the digital sampling circuit to obtain a first set of one or more digital samples. The digital sampling may be triggered by a reference signal generated by the LIDAR system. The reference signal may include a clock signal synchronized with or associated with the generation or transmission of the two or more light pulses obtained at 505. In another example, a second portion of the electrical signal indicative of the second light pulse is received by the digital sampling circuit and sampled at an adjusted sampling time to obtain a second set of one or more digital samples, each sample in the second digital sample set being offset from a corresponding sample in the first digital sample set by a time delay. Sampling at an adjusted sample timing may include adjusting the reference signal, or another timing signal configured to operate the digital sampling circuit, to introduce a time delay that either advances or delays triggering or operating the digital sampling circuit to obtain the second set of digital samples. Sampling with adjusted sample timing may include any other technique for shifting or offsetting (e.g., delaying or advancing) the trigger or sample time for acquiring the second digital sample set relative to the trigger or digital sample time for acquiring the first digital sample set. The sampling times of portions of the electrical signal corresponding to different optical pulses may be adjusted by different time delays within a specified time span or period, such as within a sampling period of a sampling circuit having a first sample rate, as described herein, such that the digital sampling circuit samples portions of the electrical signal at different times relative to a reference signal or relative to the sample time of at least one other portion of the electrical signal.

[0040] At 520, a temporal profile, or a reference waveform indicative of a temporal profile, of the optical pulse acquired at 505 is acquired using the first and second sets of one or more digital samples. The temporal profile includes an estimate of both the temporal and amplitude shape of the acquired optical pulse. In one example, generating the temporal profile includes generating a first temporal profile using the first set of digital samples and updating the first temporal profile using the second set of digital samples to acquire a second temporal profile. Generating the first temporal profile can include storing the digital samples in electronic memory associated with or accessible by a process configured to retrieve samples according to a time index or parameter. Updating the first temporal profile, in one example, includes storing the second set of digital samples in electronic memory such that the process can retrieve samples from the first and second sets of digital samples according to a time index or parameter, where successive time index or parameter values ​​are indexed and interleaved samples are retrieved from the electronic memory. In another example, updating the first temporal profile includes combining the first set of digital samples with the second set of digital samples using one or more mathematical or logical operations, such as averaging, and generating the second temporal profile using the combined samples according to any of the techniques described herein. In yet another example, updating the first temporal profile includes generating an interim temporal profile using the second set of digital samples and combining the interim temporal profile with the first temporal profile to obtain the second temporal profile.

[0041] In one example, the first and second sets of digital samples are combined in a time-indexed array or other data structure according to the time delay associated with each sample set. The combined samples are then processed using suitable digital signal processing techniques to generate a temporal profile of the acquired optical pulse at 505. Such processing may include one or more filtering, upsampling, or interpolation techniques or operations. In one example, the generated temporal profile comprises a data structure, such as a time-indexed table or array, that includes one or more sampled, interpolated, or filtered data points that indicate the time-varying amplitude or signal intensity of the acquired optical pulse at 505. In one example, the generated temporal profile has a higher resolution than the sample rate or sampling resolution of the detectors used to capture the first and second optical pulses.

[0042] In 525, at least one light pulse is transmitted toward the target area, for example, by transmitter 105. The at least one light pulse can be transmitted toward one or more spatial points within the target area, such that the one or more light pulses scan the target area according to a two-dimensional pattern at a specified spatial resolution. In one example, transmitting the at least one light pulse includes acquiring a light pulse from an illuminator, such as illuminator 110, processing the acquired light pulse through an optical device, such as splitter 115, to split or divide the light pulse into first and second light pulses, and transmitting the first light pulse (e.g., reference pulse 117) to a photodetector, such as detector 125, while transmitting the second light pulse (e.g., transmit pulse 116) toward the target area through a lens configured to emit light pulses generated by, for example, a LIDAR system. In another example, transmitting the at least one light pulse includes acquiring a light pulse from the illuminator and transmitting the unmodulated light pulse through a lens toward the target area.

[0043] At 530, a reflection of the at least one light pulse transmitted at 525 is received from the target area at a second detection circuit, such as detector 180. Receiving the reflection of the at least one light pulse can include operating a sampling circuit, such as sampling circuit 185, to capture one or more digital samples of the amplitude or intensity of the reflected light pulse at a second sample rate. In one embodiment, the sampling circuit that acquires the digital samples of the reflection of the at least one light pulse has a sample rate (e.g., a second sample rate) that is higher than the sample rate (e.g., the first sample rate) of the sampling circuit that acquires the digital samples of the received light pulse at 510. In another embodiment, the sampling circuit that acquires the digital samples of the reflection of the at least one light pulse has a sample rate that is comparable to, similar to, or approximately equal to the temporal resolution of the temporal profile generated at 520. In yet another embodiment, the sampling circuit that acquires the digital samples of the reflection of the at least one light pulse has a sample rate that is lower than the temporal resolution of the temporal profile generated at 520.

[0044] At 535, an arrival time of a reflection of the at least one optical pulse is determined based on the temporal profile generated at 520. In one embodiment, the arrival time of the at least one optical pulse is determined by adjusting one or more coefficients of a filter circuit, such as a matched filter circuit, based on the temporal profile and processing digital samples of the reflection of the at least one optical pulse using the adjusted filter circuit to, for example, determine a time at which there is maximum overlap between the digital samples and the temporal profile. In one embodiment, adjusting the coefficients of the filter circuit includes determining the coefficients of the filter circuit using one or more sampled, interpolated, or filtered data points obtained from the temporal profile.

[0045] Set of operations 500 may include any other operations, or any other suitable sequence of operations, suitable for implementing the techniques described herein. In one example, set of operations 500 includes receiving a first pulse and a second pulse at a first detector, as described at 510; adjusting a sampling time or trigger for initiating sampling of each pulse to introduce different time delays between sets of digital samples taken from each pulse; determining a temporal profile or intermediate reference waveform based on each set of digital samples; combining each temporal profile or intermediate reference waveform to generate a combined temporal profile or reference waveform, for example, by averaging the temporal profiles or intermediate reference waveforms; and using the combined temporal profile or reference waveform in a matched filter as described herein. In another example, set of operations 500 includes sampling the first and second optical pulses, as described at 515, at a sample rate lower than the sample rate at which reflections of at least one optical pulse are sampled at 530. In another embodiment, the set of operations 500 includes upsampling the set of digital samples of the reflection of at least one optical pulse based on or to match the resolution of the temporal profile generated in 520 before determining the time of arrival in 530.

[0046] One or more of the operations in set of operations 500 may be performed in a different order than described herein. In one example, one or more of operations 510, 515, and 520 may be performed before, after, or in parallel with one or more of operations 525, 530, and 535. In one example, the time is generated or updated in parallel with transmitting at least one light pulse to the target area or receiving a reflection of at least one light pulse from the target area. In another example, the time profile is continuously updated by acquiring and processing additional light pulses as described in operations 505, 510, 515, and 510.

[0047] Various Examples Example 1 is a method for determining a distance to a target area in an optical detection system, the method including: acquiring first and second light pulses from an optical transmitter; providing the first and second light pulses to a first detector in the optical detection system; adjusting a sample time of the second light pulse to create a time delay between capturing a sample of the first light pulse and capturing a sample of the second light pulse at the first detector; capturing samples of each of the first and second light pulses at the first detector based on the adjusted sample time; acquiring a temporal profile of the captured samples; transmitting a third light pulse to the target area; receiving a reflection of the transmitted third pulse from the target area at a second detector; and determining a time of arrival of the received reflection based on the temporal profile.

[0048] In Example 2, the subject matter of Example 1 includes wherein the third light pulse and at least one of the first and second light pulses are obtained from a common light pulse.

[0049] In Example 3, the subject matter of Example 2 includes obtaining the third light pulse and at least one of the first and second light pulses by sending the common light pulse through an optical beam splitter to split the common light pulse into the third light pulse and at least one of the first and second light pulses.

[0050] In Example 4, the subject matter of Examples 1-3 includes wherein adjusting the sample time of the second light pulse to create a time delay between capturing a sample of the first light pulse at the first detector and capturing a sample of the second light pulse includes adding a time delay to a sampling clock of a converter circuit configured to capture digital samples of the received light pulse at the first detector.

[0051] In Example 5, the subject matter of Examples 1-4 includes wherein adjusting the sample time of the second light pulse to create a time delay between capturing a sample of the first light pulse at the first detector and capturing a sample of the second light pulse includes introducing a time delay in an arrival time of the second light pulse at a converter circuit configured to capture a digital sample of the light pulse received at the first detector.

[0052] In Example 6, the subject matter of Examples 1-5 includes where capturing the respective first and second light pulses with the first detector based on the adjusted sample times includes capturing one or more samples of a first set of the first light pulse at the sample time of the first light pulse, and capturing one or more samples of a second set of the second light pulse at an adjusted sample time of the second light pulse, where the adjusted sample time of the second light pulse is delayed by a time delay relative to the sample time of the first light pulse.

[0053] In Example 7, the subject matter of Example 6 includes the first detector having a first sample rate, and acquiring a temporal profile of the captured samples includes interleaving one or more samples of a first set with one or more samples of a second set to acquire a temporal profile having a higher temporal resolution than the first sample rate.

[0054] In Example 8, the subject matter of Examples 1-7 includes, wherein a time delay between capturing a sample of the first light pulse and capturing a sample of the second light pulse with the first detector is less than a sampling period of the first detector.

[0055] In Example 9, the subject matter of Examples 1-8 includes upsampling samples of reflections received from the target area of ​​the transmitted third pulse based on the temporal profile of the captured samples before determining the arrival times of the received reflections based on the temporal profile.

[0056] In Example 10, the subject matter of Examples 1-9 includes adjusting coefficients of a matched filter based on the determined temporal profile of the captured samples, and determining, using the matched filter, a time of arrival of a reflection received from the target area of ​​the transmitted third pulse.

[0057] In Example 11, the subject matter of Examples 1-10 includes, wherein the temporal profile of the captured sample includes an estimate of the shape of the first and second light pulses.

[0058] Example 12 is an optical ranging system for determining a distance to a target area, the system comprising: a transmitter circuit for generating first and second optical pulses; a first optical detection circuit for converting the first and second optical pulses into respective first and second electrical signals; a sampling circuit coupled to the first optical detector for acquiring samples of the electrical signals; a modulation circuit coupled to the sampling circuit, the modulation circuit activating the sampling circuit to acquire a first sample of the first electrical signal according to a first sampling trigger and to acquire a second sample of the second electrical signal according to a second sampling trigger, the first sampling trigger being offset in time from the second sampling trigger by a timing delay corresponding to a fraction of a sampling period of the first detector; a synthesizer circuit for interleaving the first and second samples to generate a reference waveform, thereby acquiring a reference waveform having a higher resolution than the sampling resolution of the first detection circuit; and a signal detection circuit for determining the arrival time of a reflection of a third optical pulse from the target area based on the reference waveform.

[0059] In Example 13, the subject matter of Example 12 includes the transmitter circuit including one or more circuits for transmitting a third light pulse to the target area, and the system further including a second detection circuit for converting a reflection of the third light pulse into a third electrical signal.

[0060] In Example 14, the subject matter of Examples 12-13 includes the system further comprising an optical splitter for obtaining a third optical pulse and at least one of the first and second optical pulses from the common optical pulse.

[0061] In Example 15, the subject matter of Examples 12-14 includes, wherein the system further comprises a delay circuit coupled to the sampling circuit for obtaining a time delay between the first sampling trigger and the second sampling trigger.

[0062] In Example 16, the subject matter of Examples 12-15 includes, wherein the synthesis circuitry includes an averaging circuitry for averaging each of the first and second samples to obtain the reference waveform.

[0063] In Example 17, the subject matter of Examples 12-16 includes the signal detection circuit comprising: a second optical detection circuit for receiving a reflection of the third light pulse from the target area; a filter circuit coupled to the second detection circuit and the synthesizer circuit; and a second circuit for adjusting one or more components of the filter circuit based on a reference waveform to obtain an adjusted filter circuit, and for determining the arrival time of the reflection of the third light pulse using the adjusted filter.

[0064] Example 18 is a method for determining a distance to a target area in an optical detection system, the method including: acquiring first and second light pulses from a signal generator in the optical detection system; acquiring samples of each of the first and second light pulses, the samples having a first temporal resolution; generating a reference waveform having a second temporal resolution by combining the samples of each of the first and second light pulses, the second temporal resolution being higher than the first temporal resolution; acquiring a reflection of a third light pulse from the target area; and using the reference waveform to determine the arrival time of the reflection of the third light pulse.

[0065] In Example 19, the subject matter of Example 18 includes capturing one or more samples of a first set of a first light pulse at a sample time of the first light pulse, and capturing one or more samples of a second set of a second light pulse at an adjusted sample time of a second light pulse, where the adjusted sample time of the second light pulse is delayed relative to the sample time of the first light pulse by a time delay that is less than a sampling period of a detection circuit configured to obtain samples of each of the first and second light pulses.

[0066] In Example 20, the subject matter of Examples 18-19 includes wherein combining samples of the respective first and second optical pulses includes interleaving samples of the respective first and second optical pulses to obtain a reference waveform having a second temporal resolution.

[0067] In Example 21, the subject matter of Examples 18-20 includes where determining the arrival time of the reflection of the third optical pulse using the reference waveform includes obtaining a matched filter based on the reference waveform; and processing the sample of the reflection of the third optical pulse using the matched filter to determine an overlap between the matched filter and the sample of the reflection of the third optical pulse.

[0068] Example 22 is at least one machine-readable medium comprising instructions that, when executed by a processing circuit, cause the processing circuit to perform operations to implement any of Examples 1 to 21.

[0069] The twenty-third embodiment is an apparatus including means for implementing any one of the first to twenty-first embodiments.

[0070] The twenty-fourth embodiment is a system for implementing any one of the first to twenty-first embodiments.

[0071] Example 25 is a method for implementing any of Examples 1 to 21.

[0072] Each of the above non-limiting aspects can stand on its own or can be combined in various permutations or combinations with one or more of the other aspects or other subject matter described in this document.

[0073] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also generally referred to as "examples." Such examples may include elements in addition to those shown or described. However, the inventors also contemplate examples in which only the elements shown or described are provided. Furthermore, the inventors also contemplate examples using any combination or permutation of the elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof) or with respect to other examples (or one or more aspects thereof) shown or described herein. In the event of inconsistent usage between this document and any document incorporated by reference, the usage in this document controls.

[0074] In this document, the terms "a" or "an" are used to include one or more than one, as is common in patent documents, regardless of any other examples, or the usage of "at least one" or "one or more." In this document, the term "or" is used to refer to a non-exclusive "or," such that "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise specified. In this document, the terms "including" and "in which" are used as the plain English equivalents of the respective terms "comprising" and "wherein." Additionally, the terms "can" or "can include" are used liberally to indicate that, in some embodiments, an element includes the associated element, or, in other embodiments, an element optionally includes or omits elements. Also, in the following claims, the terms "comprises" and "comprising" are open-ended, i.e., systems, devices, articles, compositions, formulations, or processes that include elements in addition to those recited after such terms in a claim are still considered to be within the scope of that claim. Furthermore, in the following claims, terms such as "first," "second," and "third" are used merely as labels and are not intended to impose numerical requirements on their objects.

[0075] Method embodiments described herein may be at least partially machine- or computer-implemented. Some embodiments may include a computer-readable or machine-readable medium encoded with instructions operable to configure an electronic device to perform a method such as described in the above embodiments. Such method implementations may include code, such as microcode, assembly language code, high-level language code, etc. Such code may include computer-readable instructions for performing various methods. The code may form part of a computer program product. Furthermore, in one embodiment, the code may be tangibly stored, for example, during execution or at other times, on one or more volatile, non-transitory, or non-volatile tangible computer-readable media. Examples of these tangible computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memory (RAM), read-only memory (ROM), etc.

[0076] The above description is illustrative, not limiting. For example, the above examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments may be employed, for example, by one of ordinary skill in the art, upon reviewing the above description. The Abstract is provided in accordance with 37 C.F.R. §1.72(b) to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be construed as intending that any unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in fewer than all features of a particular disclosed embodiment. Accordingly, it is contemplated that the following claims will be incorporated into the Detailed Description as an example or embodiment, with each claim standing on its own as a separate embodiment, and that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full range of equivalents to which such claims are entitled. [Explanation of symbols]

[0077] 100 systems 105 Transmitter 110 Irradiator 115 Beam Splitter 116 First Light Pulse 117 Second Light Pulse 117 Reference Pulse 120 Reference circuit 125 detector 130 Sampling Circuit 135 Adjustment circuit 140 Converter Circuit 145 Reference waveform generator 150 control circuit 155 memory 156 filters 160 Synthesizer 165 Noise Reduction Filter 170 Receiver Circuit 175 Signal Detector 176 Return Signal 180 detectors 185 Sampling Circuit 190 Sampling Circuit 195 Converter Circuit 197 Noise Reduction Filter 205 First Electric Pulse 210 Reference Trigger 215 First Sample 220 samples 225 samples 230 Second Electric Pulse 235 Digital Samples 240 Second Sample 245 Third Sample 250 Third Electric Pulse 255 First Sample 260 Second Sample 265 Third Sample 310 Filter 315 Filtered Reference Waveform 405 Digital Sample Set 410 Interpolator 415 Enhanced Digital Sample Set 420 Synthesis reference waveform 425 Matched Filter

Claims

1. 1. A method for determining a distance to a target area in an optical detection system, comprising: obtaining first and second optical pulses from an optical transmitter; providing the first and second light pulses to a first detector in the optical detection system; adjusting a sample time of the second light pulse to create a time delay between capturing a sample of the first light pulse at the first detector and capturing a sample of the second light pulse, the time delay comprising adding a time delay to a sampling clock of a converter circuit configured to capture digital samples of the light pulse received at the first detector; capturing a sample of each of the first and second light pulses with the first detector based on the adjusted sample time; obtaining a temporal profile of the captured sample; transmitting a third pulse of light to the target area; receiving, with a second detector, a reflection of the transmitted third pulse from the target area and determining a time of arrival of the received reflection based on the temporal profile; A method comprising:

2. The method of claim 1 , wherein the third light pulse and at least one of the first and second light pulses are obtained from a common light pulse.

3. 3. The method of claim 2, further comprising obtaining the third light pulse and at least one of the first and second light pulses by sending the common light pulse through an optical beam splitter to split the common light pulse into the third light pulse and at least one of the first and second light pulses.

4. 2. The method of claim 1, wherein adjusting the sample time of the second light pulse to create the time delay between capturing the sample of the first light pulse and capturing the sample of the second light pulse at the first detector comprises introducing a time delay in the arrival time of the second light pulse at a converter circuit configured to capture digital samples of light pulses received at the first detector.

5. 2. The method of claim 1 , wherein capturing the first and second respective light pulses with the first detector based on the adjusted sample time comprises: capturing one or more samples of a first set of the first light pulse at a sample time of the first light pulse; and capturing one or more samples of a second set of the second light pulse at the adjusted sample time of the second light pulse, wherein the adjusted sample time of the second light pulse is delayed by the time delay with respect to the sample time of the first light pulse.

6. 6. The method of claim 5, wherein a first detector has a first sample rate, and wherein obtaining the temporal profile of the captured samples comprises interleaving one or more samples of the first set with one or more samples of the second set to obtain a temporal profile having a higher temporal resolution than the first sample rate.

7. 2. The method of claim 1, wherein the time delay between capturing the sample of the first light pulse and capturing the sample of the second light pulse with the first detector is less than a sampling period of the first detector.

8. 2. The method of claim 1, further comprising upsampling samples of the received reflections from the target area of ​​the transmitted third pulse based on the temporal profile of the captured samples before determining a time of arrival of the received reflections based on the temporal profile.

9. adjusting coefficients of a matched filter based on the determined temporal profile of the captured samples; determining the time of arrival of the received reflection of the transmitted third pulse from the target area using the matched filter; The method of claim 1 further comprising:

10. The method of claim 1 , wherein the temporal profile of the captured sample includes an estimate of the shape of the first and second light pulses.

11. 1. An optical ranging system for determining a distance to a target area, comprising: a transmitter circuit for generating first and second light pulses; a first optical detection circuit for converting the first and second optical pulses into respective first and second electrical signals; a sampling circuit coupled to the first optical detector for obtaining a sample of the electrical signal; a modulation circuit coupled to the sampling circuit, the modulation circuit activating the sampling circuit to obtain a first sample of the first electrical signal according to a first sampling trigger and to obtain a second sample of the second electrical signal according to a second sampling trigger, the first sampling trigger being offset in time from the second sampling trigger by a timing delay corresponding to a fraction of a sampling period of the first detector; a synthesizer circuit for interleaving the first and second samples to generate a reference waveform, thereby obtaining the reference waveform having a resolution higher than the sampling resolution of the first detection circuit; a signal detection circuit for determining the arrival time of a reflection of a third light pulse from the target area based on the reference waveform; A system comprising:

12. 12. The system of claim 11, wherein the transmitter circuitry includes one or more circuits for transmitting the third light pulse to the target area, the system further comprising a second detection circuit for converting the reflection of the third light pulse into a third electrical signal.

13. 12. The system of claim 11, further comprising an optical splitter for obtaining the third optical pulse and at least one of the first and second optical pulses from a common optical pulse.

14. The system of claim 11 , further comprising a delay circuit coupled to the sampling circuit for obtaining a time delay between the first sampling trigger and the second sampling trigger.

15. 12. The system of claim 11, wherein the synthesizer circuit comprises an averaging circuit for averaging the respective first and second samples to obtain the reference waveform.

16. The signal detection circuit a second optical detection circuit for receiving the reflection of the third light pulse from the target area; a filter circuit coupled to the second detection circuit and the synthesizer circuit; a second circuit for adjusting one or more components of the filter circuit based on the reference waveform to obtain an adjusted filter circuit, and for determining the arrival time of the reflection of the third light pulse using the adjusted filter; The system of claim 11 , comprising:

17. 1. A method for determining a distance to a target area in an optical detection system, comprising: obtaining first and second light pulses from a signal generator within the optical detection system; acquiring a sample of each of the first and second light pulses, the sample having a first temporal resolution; generating a reference waveform having a second temporal resolution by combining the samples of the first and second respective optical pulses, the second temporal resolution being greater than the first temporal resolution; obtaining a reflection of a third light pulse from the target area; determining a time of arrival of the reflection of the third light pulse using the reference waveform; A method comprising:

18. capturing a first set of one or more samples of the first light pulse at a sample time of the first light pulse; capturing a second set of one or more samples of the second light pulse at an adjusted sample time of the second light pulse, the adjusted sample time of the second light pulse being delayed relative to the sample time of the first light pulse by a time delay that is less than a sampling period of a detection circuit configured to obtain the samples of each of the first and second light pulses; 20. The method of claim 17, further comprising:

19. 18. The method of claim 17, wherein combining the samples of the respective first and second light pulses comprises interleaving the samples of the respective first and second light pulses to obtain the reference waveform having the second temporal resolution.

20. determining the time of arrival of the reflection of the third light pulse using the reference waveform; deriving a matched filter based on the reference waveform; processing the samples of the reflection of the third pulse of light using the matched filter to determine an overlap between the matched filter and the samples of the reflection of the third pulse of light; 18. The method of claim 17, comprising:

21. A method for determining a distance to a target area in an optical detection system, comprising: obtaining first and second optical pulses from an optical transmitter; providing the first and second light pulses to a first detector in the optical detection system; adjusting a sample time of the second light pulse to create a time delay between capturing a sample of the first light pulse and capturing a sample of the second light pulse with the first detector; capturing one or more samples of a first set of the first light pulse at a sample time of the first light pulse and capturing one or more samples of a second set of the second light pulse at the adjusted sample time of the second light pulse, wherein the adjusted sample time of the second light pulse is delayed by the time delay with respect to the sample time of the first light pulse; obtaining a temporal profile of the captured sample; transmitting a third pulse of light to the target area; receiving, with a second detector, a reflection of the transmitted third pulse from the target area and determining a time of arrival of the received reflection based on the temporal profile; A method comprising:

22. The method of claim 21, wherein the first detector has a first sample rate, and obtaining the temporal profile of the captured samples includes interleaving one or more samples of the first set with one or more samples of the second set to obtain a temporal profile having a higher temporal resolution than the first sample rate.

23. The method described in claim 21, wherein the third light pulse and at least one of the first and second light pulses are obtained from a common light pulse.

24. The method of claim 23, further comprising obtaining the third light pulse and at least one of the first and second light pulses by transmitting the common light pulse through an optical beam splitter to split the common light pulse into the third light pulse and at least one of the first and second light pulses.

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